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Memorable Comets

Comet Finlay

    15P/Finlay is a memorable comet to us Japanese. Back in October 1919, Mr.Tetsuo Sasaki, who was an assistant at Kyoto University's Kwasan Observatory, found by chance a 9th-magnitude comet in Capricornus while observing at the observatory's yard. It turned out to be a return of Comet Finlay. Subsequently, the comet was named Comet Finlay-Sasaki. In those days, there was a rule that allowed both discoverer's and recoverer's names to be used, though the recoverer's name was added only during the comet's particular apparition.
    Mr. Sasaki died young, but this comet returned many times after his death. Each time it returned, Mr. Sasaki's achievement was talked about and passed on to next generations of observers.
    Since I began my comet search in 1950, I had also conducted photographic observations. In those days, it was extraordinary for amateur astronomers to attempt a systematic search to recover periodic comets. Not long after my observatory was moved to Geisei village under dark skies from my residence in Kochi, Comet Finlay returned.
    This is July 2008 and I am writing this story, while Comet Finlay is glowing in the predawn sky. I have been observing this comet with Geisei's 70cm reflector since the end of June. It was in the second half of June, 1974, when I recovered this comet at Geisei. The conditions were the same as this year. At an extremely low altitude in the morning twilight immediately before the daybreak, the 15th-magnitude comet was casting its faint light on the 21cm mirror. The discovery was immediately reported by a telegram to Tokyo Astronomical Observatory, which was in turn sent to observatories across the country as well as to the Smithsonian half way around the world. In those days there was no FAX nor Internet.
    I found a photograph taken at that time without any data accompanying it. The time of the discovery was 3:40 am on June 25, 1974, Japan Standard Time. I have a number of photographs taken that day and the following day. This photograph must be one of those taken on the day of the discovery with Kodak's 103a-o glass plate using a 21cm f/5 telescope (Kojima mirror). The skies those days were excellent and 103a-o plates were very effective. It had been developed exclusively for astronomical use with very little reciprocity failure. A series of recovery of periodic comets at Geisei owes much to Kodak's photographic plates. They could easily compete with today's CCDs.

Copyright (C) 2008 Geisei Observatory

10-minute exposure from 3:32, July 16, J.S.T.
70cm f/7 reflector, TMY400 film

Copyright © 2010 Tsutomu Seki.